Degradation of ultra high molecular weight polyethylene (hereafter, polyethylene) joint replacement components after gamma irradiation in air continues to be recognized as a significant clinical problem limiting the longevity of total joint arthroplasties, which represent the standard of care for patients with advanced degenerative joint disease. Oxidative degradation of polyethylene has been associated with accelerated wear, brittle fracture, and delamination of total joint replacement components. Although it is now recognized that the degradation of polyethylene plays an important role in the damage mechanisms of orthopaedic components, it is still unclear the extent to which the mechanical degradation of polyethylene relates to the overall clinical performance of total hip arthroplasty, due in part to the logistical difficulty in tracing the sterilization and shelf aging history of the components, and also due to the experimental difficulty in directly measuring the mechanical behavior of retrieved implants. The range of mechanical behavior associated with traceable, clinically retrieved orthopedic components is critically needed to guide the development of improved polyethylenes, such as the highly crosslinked polyethylenes which have recently been introduced into clinical practice for total hip arthroplasty. The purpose of this proposed research is to examine the influence of mechanical degradation after implantation on the clinical performance of metal-backed acetabular components for total hip arthroplasty.